Characteristics And Control Measures Of Agricultural Non-point Source Pollution In The Upper Beiyun River Basin

The Beiyun River originates from the western mountainous area of Beijing and flows through Beijing urban area and Tong Zhou Sub-center,which responsible for water supply,flood control,landscape and culture.The upper Beiyun River basin include Beisha River,Dongsha River and Nansha River.The water ecological environment problems are prominent in Beijing-Tianjin-Hebei region centered on the Beiyun River basin:serious water pollution,water quality has exceeded the level V that has high proportion,wide range and high intensity of black odor water bodies,water and soil are lossing,river cut off and other factors jointly cause the extreme degradation of the basin ecosystem.This paper adopted the upper of Beiyun River basin as the research object,carried out the monitoring and analysis of rainfall,runoff and non-point source pollution characteristics of typical fields.This thesis obtains the runoff characteristics,pollutant concentration process,pollution load and the effect of pollution reduction measures of typical fields under typical rainfall.The main conclusions are as follows:（1）The results show that the runoff depth and runoff coefficient are village land>agricultural land>Natural Forest and grassland.（2）According to the water quality analysis results of different types of land use under typical rainfall,NH₃-N in runoff is within level II of surface water;The concentrations of TN,TP and COD in agricultural runoff are higher than those in rural land,forest and grassland,and the concentration process is related to the rainfall process.Among them,the TP concentration in agricultural exceeds the level V water limit of surface water.（3）According to the non-point source pollution load estimated by the output coefficient model,the pollution load of agricultural land and rural land is serious,which should be paid more attention.Based on the calculation results of pollution load error,the values of various parameters involved in the output coefficient model have a certain reference significance for the calculation of agricultural non-point source pollution in the upper reaches of the upper Beiyun River basin.（4）The analysis results of initial scouring effect show that agricultural land and natural forest and grassland have different degrees of the effect of first flush.Due to the high treatment intensity of villages and towns,there is no effect of first flush in this study.（5）According to the experimental study on the effect of agricultural non-point source pollution reduction measures in typical fields:gravel filter belt,coconut fiber roll filtration,and natural hedgerow have good effects on agricultural non-point source pollution reduction.From the source to the end of the ecological ditch,it is generally in a reduced state,and has good popularization value.